This invention relates to an electrophotographic apparatus comprising an electrostatic charge retentive drum which includes a drum-shaped substrate made of electrically conductive material and a charge retentive layer applied on the surface of the drum-shaped substrate, means for transferring a toner image formed on the charge retentive layer onto a record carrier and means for peeling the record carrier from the charge retentive layer after the toner image has been transferred thereon.
Various electrophotographic apparatuses of the above mentioned kind have been proposed and realized. The applicant has also developed an electrophotographic apparatus comprising a photosensitive drum which includes a rotating drum substrate made of metal and a photosensitive layer applied on the drum, means for forming an electrostatic charge image on the drum, means for developing the charge image with toner to form a toner image, means for transferring the toner image onto a record paper and means for fixing the transferred toner image on the record paper. In such an apparatus the photosensitive drum should have the following functions;
(1) the toner image of excellent quality can be formed, PA1 (2) the toner image can be transferred efficiently without deteriorating the toner image, PA1 (3) the record paper which is fed with being in intimately contact with the drum can be positively peeled off, PA1 (4) the photosensitive drum can be easily exchanged.
Heretofore various methods for peeling the record paper off the drum have been known. The most simple and positive method is to use a peeling claw. In order to peel the record paper off the drum much more positively it has been also known to form a recess or depressed portion on the drum surface along a trajectory of the peeling claw and a free end of peeling claw is inserted in the recess, so that the end of peeling claw can be positively positioned underneath the record paper. That is to say the free end of peeling claw creeps under a front surface of the record paper on which surface the toner image has been transferred.
On the other hand in order to obtain stably a duplicated image of good quality the electrically conductive drum substrate should be always maintained at the stable earth potential. For instance, in a Japanese Patent Laid-Open Publication No. 74,234/73 on respective sides of the photosensitive drum are secured flange members made of metal and these flange members are journaled on a stationary shaft made of metal by means of ball bearing members also made of metal. In such an apparatus the drum substrate is electrically connected to the earth potential through the flange members, bearing members and stationary shaft. Further the photosensitive drum is driven by a pin-clutch hole engagement, the pin being secured to a driving gear arranged coaxially with the shaft and the hole being formed in one of the flange members. Upon exchanging the photosensitive drum it is necessary to withdraw the dram assembly along the stationary shaft. During this withdrawing operation the bearing member secured to the flange member slides on the stationary shaft.
In the above mentioned known photosensitive drum assembly since the stationary shaft and bearing member have to be made of metal and thus the bearing member does not smoothly slide on the shaft and particularly when the apparatus has been remained inoperative for a relatively long time the flange and bearing members and/or the bearing member and stationary shaft, respectively might be fastened to each other with rust. As a result thereof the earth potential on the conductive drum might be unstable and the exchange of the drum becomes very difficult. Moreover since the flanges and bearings are made of metal they are very heavy and thus the photosensitive surface of drum is quite liable to be injured during the exchange thereof. The flange and driving gear are made as separate bodies and have complicated construction. From the view point of economy they could not be manufactured as an integral body of metal.